1. Technical Field of the Invention
This invention relates to a novel method and apparatus for the dispersion of sediment, such as hydrocarbon sludge in a storage tank. More particularly, this invention relates to a method and apparatus for cleaning the interior of hydrocarbon storage tanks of the type used in petroleum refineries, chemical plants and the like for storing large volumes of hydrocarbon liquids, wherein solid materials (composed principally of hydrocarbons) and normally referred to as "hydrocarbon sludge" accumulate with the passage of time.
Still more particularly, this invention relates to novel apparatus for dispersing accumulated sediments, such as hydrocarbon sludge, in a storage tank, such apparatus comprising a hollow housing, liquid agitation means including a plurality of nozzled outlet jets laterally rotatably mounted on the housing in fluid communication with the hollow interior thereof, connecting means comprising an independently rotatable tubular casing rotatably mounted on the housing in fluid communication with the interior thereof, the tubular casing having casing turning means, such as a kelly, mounted therein and having casing turning means mounted thereon and being operatively connected with the nozzled outlet jets, and multi-joint support pipe means rotatably jointed to the connecting means in fluid communication with the interior of the tubular casing.
With this construction, an appropriate pump means may be provided for forcing a liquid, such as a liquid hydrocarbon through the multi-joint support pipe means and the tubular connecting means into the hollow housing and out of the hollow housing through the nozzled outlet jets and indexing power means may suitably be provided and operatively connected with the laterally rotatable outlet jets in a manner to be described in order to laterally rotate the nozzled outlet jets at a predetermined rate independent of the rate of flow of liquid through the nozzled outlet jets.
In a preferred embodiment, the liquid circulator will also comprise an elongate sled and the hollow housing will be pivotally mounted on the sled adjacent the front end thereof. The mass of the sled should be greater than the mass of a combination of the hollow housing, the liquid agitating means and the connecting means so that the center of gravity of the sled and the said combination mounted thereon is below the lateral axis of the opening in the housing and the tubular connecting means mounted thereon. As a consequence the liquid agitation means will always be in an upright position.
In accordance with one embodiment of the present invention, a gate valve and an isolation barrel are fixed to a manway in the side of a storage tank, such as a storage tank of the type used to store crude oil. Representative crude oil storage tanks have a diameter of about 100 to about 300 feet and a height of about 20 to about 50 feet. Hydrocarbon sludge will settle from the stored crude oil with the passage of time such that the bottom of a crude oil storage tank may contain an accumulation of about 1 to about 10 feet of hydrocarbon sludge in the bottom of the crude oil storage tank. In accordance with this embodiment of the present invention, an isolation barrel is mounted on the gate valve, the isolation barrel being provided with a valve-controlled drain line in the side thereof and a tubular packing gland in the closed rear end thereof. With the gate valve closed, a crude oil circulator of the present invention may be placed in the isolation barrel. After the crude oil circulator is positioned in the isolation barrel and the isolation barrel is mounted on the gate valve, the gate valve may be opened and crude oil in the storage tank will flow into the isolation barrel. The first joint of pipe connected to the laterally nozzled hydrocarbon sludge circulator will suitably contain a rotatable kelly rod or other suitable interconnective turning means. A plurality of additional joints of pipe, each of which contains interconnective turning means is sequentially coupled to the first joint of pipe and pushed through the packing gland of the isolation barrel, thereby progressively forcing the crude oil circulator into the crude oil storage tank. When the crude oil circulator has been forced into the storage tank a desired distance, a connecting rod is coupled to the interconnective turning means.
In further accordance with this embodiment, the valved drain line of the isolation barrel is fluidly interconnected with a suitable filter means which is, in turn, fluidly interconnected with the suction side of a high pressure liquid pump. The discharge side of the high pressure liquid pump is fluidly interconnected with the plurality of joints of pipe coupled to the liquid (crude oil) circulator. Indexing power means are operatively interconnected with the connecting rod. With this arrangement, operation of the high pressure liquid pump will cause a stream of crude oil to be drawn from the isolation barrel through the drain line to the filter means, and after filtration, to the suction side of the high pressure liquid pump. The crude oil will be pressured in the pump and discharged therefrom through the joints of pipe back to the liquid circulator and out the nozzled outlet jets into the storage tank.
Simultaneous operation of the indexing power means will rotate the connecting rod which will rotate the interconnective turning means and the casing turning means in the connecting means. As a consequence, the tubular housing and the nozzle drive means will rotate and thereby rotate the nozzled outlet jets. The resultant agitation of the crude oil in the storage tank will cause the sediment in the tank to be dispersed therein for passage from the storage tank through the isolation barrel to the filter means.
In another aspect, the present invention is directed to a method for the dispersion of hydrocarbon sludge in crude oil stored in a crude oil storage tank, in order to clean the crude oil storage tank, the method including the steps of injecting a stream of the crude oil into the hydrocarbon sludge at a velocity of about 10,000 to about 20,000 gallons per minute to thereby disperse the hydrocarbon sludge in the crude oil while agitating the crude oil in order to maintain the dispersed hydrocarbon sludge in suspension, withdrawing a stream of crude oil containing dispersed hydrocarbon sludge from the crude oil storage tank, filtering the withdrawn suspension, pressuring the filtered crude oil and reinjecting the crude oil under pressure into the crude oil storage tank at the desired velocity.
Additional modifications, embodiments and advantages of the present invention will be hereinafter described in greater detail.
2. Prior Art
Furness et al. U.S. Pat. No. 4,407,678 discloses a sludge removal machine for removing sludge from the bottom of a storage tank which comprises a hollow body, and laterally rotatable nozzles. The sludge removal machine is suspended in a storage tank from a pipe through which a cleaning liquid may be pumped. The sludge removal machine is also provided with a "turbine" or impeller for rotating the nozzles in order to disperse sludge.
Furness et al. U.S. Pat. No. 4,685,974 is directed to a method for removing settled sludge from the bottom of a storage tank which uses apparatus of the type disclosed and claimed in Furness et al. U.S. Pat. No. 4,407,678. In accordance with the method of Furness et al., a liquid such as crude oil is pumped into a machine suspended in a storage tank adjacent a side wall thereof and which is provided with diametrically opposed lateral nozzles which are rotated in a manner such that each nozzle emits liquid during 180.degree. of its rotation to avoid impingement of liquid on the side of the tank wall to thereby suspend the sledge into liquid in the tank after which the liquid having sludge suspended therein is pumped from the tank.
Strong U.S. Pat. No. 3,586,294 is directed to a method and apparatus for creating a suspension of fine particles in a liquid in a tank using a plurality of spargers suspended above the bottom of the tank on a nonrotating lattice of feed pipes through which a liquid is pumped for emission through the sparging nozzles to suspend fine particles of sediment in the liquid for discharge from the tank on removal of the suspension.
Erdman U.S. Pat. No. 1,978,615 is directed to method and apparatus for cleaning sediment from a tank containing a fluid comprising a central manifold from which a plurality of discharge pipes radiate, each discharge pipe being provided with a plurality of discharge nozzles so that liquid may be pumped through the central manifold and out through the nozzles to roil the sediment or other foreign material at the bottom of the tank and suspend it for withdrawal through a side withdrawal pipe located above the apparatus.
Edmond et al. U.S. Pat. No. 3,953,226 is directed to a device for cleaning sediment from a hot wort tank including pipe means oscillatably suspended from the top of the tank, the oscillatable pipe means being provided at a discharge point near the bottom of the tank with one or more spray jets through which hot water may be sprayed to sweep suspended matter to a sump located on the opposite side of the storage tank for removal.
Heibo U.S. Pat. No. 3,878,857 is directed to a device for cleaning the side walls of a storage tank such as a tank located on a ship carrying crude oil. The apparatus comprises an L-shaped inlet pipe suspended from the top of the tank, a pair of diametrically opposed jets are mounted on the end of the "L" so that liquid pumped through the L-shaped inlet pipe will be forced to flow out of the pipe through one of the jets at a time. Means are provided for rotating the jet nozzles about their vertical axis and an indexing means is also provided for rotating the jetting means a fraction of a turn about a horizontal axis for each complete revolution about the vertical axis. The mechanism for accomplishing this is suitably a worm gear which operates in conjunction with a cog wheel and a blocking wheel.
Richard et al. U.S. Pat. No. 2,116,935 is directed to a method and apparatus for cleaning tanks such as railroad tank cars and comprises a pipe which is suspended vertically in the tank for rotation about a horizontal axis and which contains at the lower end thereof a reaction nozzle mounted for rotation about a horizontal axis and includes a reaction nozzle member mounted on the vertical conduit for rotation about a horizontal axis so that liquid pumped down the conduit is forced out the vertically disposed jets of the reaction nozzle. The device also includes appropriate means for slowly rotating the reaction nozzle about the vertical axis of the suspending pipe.